At 16:42 30/04/2002, Jocelyn Sérot wrote:
>Sorry to jump in the middle of this discussion, but your last remark on 
>"extensible n-tuples" drew my attention (i use to need this kind of thing
in a 
>completely different context). Can you provide references on these
>extensions of ML type systems ?

Hi Jocelyn,

I give some references below, but I have to add several caveats to my
remarks.  I don't have all these papers, so I can't check exactly what they
cover.  I believe they include similar operations on labelled records, and
these can be mapped to tuples by the SML technique of defining tuples as
records with numeric labels.  Whether that's the best approach is another
question; possibly it would be simpler to represent them as nested pairs,
as Alain Frisch suggested.  Finally, I'm not sure whether all these papers
gave type systems that were extensions of ML.

Anyway, here are the papers I had in mind.  Didier's work went on to become
Objective ML (which is why I wondered whether this operation was already
available in the system underlying OCaml).  Some of the other authors are
active on this list, and might be able to tell you more accurately whether
their work is relevant.

Dave.

Luca Cardelli and John C. Mitchell, "Operations on records", DEC SRC,
August 1989.

Mitchell Wand, "Type inference for record concatenation and multiple
inheritance", LICS 1989.

Didier Remy, "Typechecking records in a natural extension of ML", POPL 1989.

Robert Harper and Benjamin Pierce, "A record calculus based on symmetric
concatenation", POPL 1991.  [N.b. Symmetric concatenation is more complex
then simple record extension]

Atsushi Ohori, "A compilation method for ML-style polymorphic record
calculi", POPL 1992.

Didier Remy, "Typing record concatenation for free", POPL 1992.







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